1. Field of the Invention
This invention relates to land irrigation apparatus of the type employed in the agricultural industry to irrigate large areas of land, and more particularly to an improved water distribution system for use in connection with such apparatus in which water is discharged from spray heads connected to a water distribution pipe as the pipe is progressively moved above the area to be irrigated.
2. Description of the Prior Art
It has long been known to irrigate large areas of land by supporting an elongated water distribution pipe on a boom for movement over the land at a level above the top of vegetation growing on the land and to discharge water from the pipe through sprinkler heads spaced along its length to continuously apply water as the boom is progressively moved over the area to be irrigated. Water has been supplied to these water distribution pipes by various means including both pressurized water mains and movable pumps which supply water from open ditches or the like. The water distribution pipe may have one end pivotally connected to a fixed water hydrant or standpipe, and moved in a circular path about this pivot point or, alternatively, the elongated boom may be moved along a path perpendicular to its longitudinal axis, with water being supplied to the distribution pipe from a water main extending parallel to the path of movement and having hydrants at spaced intervals along its length.
In land irrigation systems of this general type, the sprinkler heads are conventionally located on the top of the water distribution pipe with the water spray from each sprinkler head being directed upwardly and outwardly to cover a generally circular pattern. The spacing of the sprinkler heads is normally substantially equal to or slightly greater than the diameter of the spray pattern anticipated, taking into consideration the spray head configuration, water pressure and the like. The water boom is then moved at a rate such that the desired amount of water is applied to the land during movement of the sprinkler heads thereover.
While the known circle and lateral movement irrigation systems are a substantial improvement over the earlier, solid set systems or manually movable systems, they have not been entirely satisfactory for all soil and climate conditions. Also, it has generally not been possible to obtain an entirely uniform distribution of water over the area due to the inherent unequal distribution resulting from the series of in-line circular pattern of water from the spray nozzles. Further, the maximum time during which water is applied to an area by such apparatus is the length of time required for the boom to traverse a distance substantially equal to the diameter of the respective circular spray patterns. Accordingly, it is sometimes necessary to either apply the water at an excessive rate which can result in crop damage due to the number and size of the droplets in the spray pattern and which can result in substantial running of water on the ground. Alternatively, the spray boom has to be moved at a very slow rate in order to avoid such water damage.
Various attempts have been made to overcome the problems in obtaining a uniform water distribution while maintaining an acceptable rate of movement of the irrigation apparatus. For example, the spacing of sprinkler heads along the water boom has been reduced so that the water spray from adjacent spray heads will fall in overlapping patterns. While this produces an improved uniformity of distribution, the water is still applied to an area along the boom having a maximum width equal to the radius of the spray pattern from an individual nozzle so that the rate of application of water is sometimes excessive.
In order to enable the water boom to be moved at an increased rate, attempts have been made to apply the water to an area extending out further from each side of the boom by providing forwardly and rearwardly extending lateral pipe sections at each water pipe outlet and mounting a sprinkler head at the distal end of each pipe section. A further modification of this arrangement has been to employ a third sprinkler head at the water pipe outlet thereby enabling the sprinkler heads on the ends of the lateral pipe sections to be spaced further apart and thereby apply water to an even greater area. In all of these arrangements known to applicant, the spray heads at each outlet from the boom were arranged in a line perpendicular to the vertical plane of the water pipe so that each of the spray heads at each outlet traversed the same area. As a result, although boom travel could be increased, no improvement was achieved in uniformity of water distribution. Also, difficulty was encountered in these devices in that rigid, heavy pipe was employed to support the additional water nozzles in cantilevered relation from the water distribution pipe and the weight of such pipe and spray heads, combined with the weight of the water in the pipe resulted in frequent failures and crop damage.